In the development of fixed wing aircraft as requirements increase for greater weight and performance additional propulsive power is required. This could often be met by the relatively easy expedient of replacing the engines with higher powered engines. However, for rotary wing aircraft this relatively simple expedient is not feasible in most instances since additional power from higher powered engines for increasing aircraft performance must pass through the main rotor transmission which has an upper limit of the amount of power which can be absorbed and is a limiting factor in adding additional power to the main rotor for propulsion and lift. Main rotor transmissions comprise complex power gear trains with severe limitations in the amount of horsepower that the power train can absorb and redesigning a main rotor transmission to accommodate even moderate increases in power is a major and expensive undertaking.